Resting mEPSPs were recorded in the presence of TTX (10-6 M) from the posterior nerve of frogs (Rana esculenta) stored at room temperature (20-22° C). Each unit was exposed to a 10° C change of the bath by means of a Peltier device with a feedback controller. The range of temperatures explored was from 8° to 30° C. mEPSP rate was estimated just before and at the end of the temperature change. When mEPSP rate was high (>100/s), the estimate was performed by means of two alternative noise analysis procedures in which the mEPSP waveform was obtained from the autoregressive (minimum phase) fit to the autocorrelation of the summated potentials. In the units where mEPSP rate was less than 300/s, the event waveform was used to construct a Wiener filter to deconvolve the signal. When transmitter release rate is higher than 300/s, the Wiener-filtering procedure becomes unreliable; therefore mEPSP frequency was determined by means of a statistical method measuring variance and skewness of the fiuctuations in membrane potential. mEPSPs rate increased with increasing temperature and viceversa, the Q10 ranging from 1.11 to 2.66. Statistical analysis of Wiener-filtered recordings performed at the different temperatures showed that mEPSP peak amplitude and time interval distributions were systematically lognormal and monoexponential, respectively. In the fibres where isolated events could be detected, the elementary waveform was evaluated by fitting the average of 20-50 mEPSPs with a modified gamma function. Both peak amplitude and time-to-peak proved to decrease on increasing temperature. Results demonstrate a limited dependence of transmitter release on temperature, which does not affect the basic mechanism of secretion. More consistent are possibly the postsynaptic effects, as suggested by the modifications in the event waveform.
TEMPERATURE EFFECTS ON THE PROPERTIES OF THE CYTONEURAL JUNCTION IN THE ISOLATED FROG LABYRINTH
PELUCCHI, Bruna;ROSSI, Marialisa
1994
Abstract
Resting mEPSPs were recorded in the presence of TTX (10-6 M) from the posterior nerve of frogs (Rana esculenta) stored at room temperature (20-22° C). Each unit was exposed to a 10° C change of the bath by means of a Peltier device with a feedback controller. The range of temperatures explored was from 8° to 30° C. mEPSP rate was estimated just before and at the end of the temperature change. When mEPSP rate was high (>100/s), the estimate was performed by means of two alternative noise analysis procedures in which the mEPSP waveform was obtained from the autoregressive (minimum phase) fit to the autocorrelation of the summated potentials. In the units where mEPSP rate was less than 300/s, the event waveform was used to construct a Wiener filter to deconvolve the signal. When transmitter release rate is higher than 300/s, the Wiener-filtering procedure becomes unreliable; therefore mEPSP frequency was determined by means of a statistical method measuring variance and skewness of the fiuctuations in membrane potential. mEPSPs rate increased with increasing temperature and viceversa, the Q10 ranging from 1.11 to 2.66. Statistical analysis of Wiener-filtered recordings performed at the different temperatures showed that mEPSP peak amplitude and time interval distributions were systematically lognormal and monoexponential, respectively. In the fibres where isolated events could be detected, the elementary waveform was evaluated by fitting the average of 20-50 mEPSPs with a modified gamma function. Both peak amplitude and time-to-peak proved to decrease on increasing temperature. Results demonstrate a limited dependence of transmitter release on temperature, which does not affect the basic mechanism of secretion. More consistent are possibly the postsynaptic effects, as suggested by the modifications in the event waveform.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
